A splendid shooting practise application produced in Finland by Ilkka Ratamo and Paavo Tikkanen.
You can train trigger release with your mobile phone everywhere and how much you like. The timing becomes more demanding when your skill to squeeze becomes better.
The RightSpot app is combatible with Nokia Lumia phones (windows 8). So far the application is only in Finnish.
You can download it free here
The feedback is awaited: firstname.lastname@example.org